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HTTP Error Response Codes

When CDN is serving your site content, you may encounter various HTTP error response codes. Each requires different actions to clear them up.

503 - Service Unavailable

A 503 error indicates that is having a problem serving your site. Please open a ticket so that we may diagnose the issue.

520 - Origin Server Unavailable

A 520 error indicates that the PoP was unable to connect to the origin server. Most likely, the issue is a firewall at the origin server which is blocking connections. This is problematic because acts as a proxy service for your domain, and requires access for uncached requests.

Try adding IPs to your firewall's allowlist (or request that your hosting provider do so). Be aware that these IPs change often, and the firewall must be kept up-to-date.

521 - Origin Server Timeout

A 521 error indicates that the connection between the PoP and your origin server timed out. This just means that there was no activity for a lengthy period of time, and the connection is assumed to be dead. Check that your origin server is up and running.

524 - Site Not Found

A 524 error appears if a site is pointed to in DNS records, but is not registered as a domain on If this is incorrect, please open a ticket for further assistance.

Last update: January 30, 2024